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8320877: Shenandoah: Remove ShenandoahUnloadClassesFrequency support

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Reviewed-by: wkemper, kdnilsen, rkennke
This commit is contained in:
Aleksey Shipilev 2023-11-29 17:25:40 +00:00
parent b68356b267
commit b65ccff357
5 changed files with 3 additions and 37 deletions
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8
src/hotspot/share/gc/shenandoah/heuristics/shenandoahAggressiveHeuristics.cpp
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@ -38,12 +38,6 @@ ShenandoahAggressiveHeuristics::ShenandoahAggressiveHeuristics(ShenandoahSpaceIn
// Aggressive evacuates everything, so it needs as much evac space as it can get
SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahEvacReserveOverflow);
// If class unloading is globally enabled, aggressive does unloading even with
// concurrent cycles.
if (ClassUnloading) {
SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 1);
}
}
void ShenandoahAggressiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
@ -63,7 +57,7 @@ bool ShenandoahAggressiveHeuristics::should_start_gc() {
}
bool ShenandoahAggressiveHeuristics::should_unload_classes() {
if (!can_unload_classes_normal()) return false;
if (!can_unload_classes()) return false;
if (has_metaspace_oom()) return true;
// Randomly unload classes with 50% chance.
return (os::random() & 1) == 1;

22
src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.cpp
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@ -54,11 +54,6 @@ ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahSpaceInfo* space_info) :
_gc_time_history(new TruncatedSeq(10, ShenandoahAdaptiveDecayFactor)),
_metaspace_oom()
{
// No unloading during concurrent mark? Communicate that to heuristics
if (!ClassUnloadingWithConcurrentMark) {
FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0);
}
size_t num_regions = ShenandoahHeap::heap()->num_regions();
assert(num_regions > 0, "Sanity");
@ -263,23 +258,10 @@ bool ShenandoahHeuristics::can_unload_classes() {
return true;
}
bool ShenandoahHeuristics::can_unload_classes_normal() {
bool ShenandoahHeuristics::should_unload_classes() {
if (!can_unload_classes()) return false;
if (has_metaspace_oom()) return true;
if (!ClassUnloadingWithConcurrentMark) return false;
if (ShenandoahUnloadClassesFrequency == 0) return false;
return true;
}
bool ShenandoahHeuristics::should_unload_classes() {
if (!can_unload_classes_normal()) return false;
if (has_metaspace_oom()) return true;
size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
// Unload classes every Nth GC cycle.
// This should not happen in the same cycle as process_references to amortize costs.
// Offsetting by one is enough to break the rendezvous when periods are equal.
// When periods are not equal, offsetting by one is just as good as any other guess.
return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0;
return ClassUnloadingWithConcurrentMark;
}
void ShenandoahHeuristics::initialize() {

1
src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.hpp
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@ -130,7 +130,6 @@ public:
virtual void choose_collection_set(ShenandoahCollectionSet* collection_set);
virtual bool can_unload_classes();
virtual bool can_unload_classes_normal();
virtual bool should_unload_classes();
virtual const char* name() = 0;

5
src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp
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@ -76,11 +76,6 @@
" compact - run GC more frequently and with deeper targets to " \
"free up more memory.") \
\
product(uintx, ShenandoahUnloadClassesFrequency, 1, EXPERIMENTAL, \
"Unload the classes every Nth cycle. Normally affects concurrent "\
"GC cycles, as degenerated and full GCs would try to unload " \
"classes regardless. Set to zero to disable class unloading.") \
\
product(uintx, ShenandoahGarbageThreshold, 25, EXPERIMENTAL, \
"How much garbage a region has to contain before it would be " \
"taken for collection. This a guideline only, as GC heuristics " \

4
test/hotspot/jtreg/gc/shenandoah/oom/TestClassLoaderLeak.java
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@ -140,14 +140,10 @@ public class TestClassLoaderLeak {
// Even when concurrent unloading is disabled, Full GC has to recover
passWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:+ClassUnloading", "-XX:-ClassUnloadingWithConcurrentMark");
passWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:+ClassUnloading", "-XX:-ClassUnloadingWithConcurrentMark", "-XX:ShenandoahUnloadClassesFrequency=0");
passWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:+ClassUnloading", "-XX:+ClassUnloadingWithConcurrentMark", "-XX:ShenandoahUnloadClassesFrequency=0");
// Should OOME when unloading forcefully disabled, even if local flags try to enable it back
failWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:-ClassUnloading");
failWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:-ClassUnloading", "-XX:+ClassUnloadingWithConcurrentMark");
failWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:-ClassUnloading", "-XX:+ClassUnloadingWithConcurrentMark", "-XX:ShenandoahUnloadClassesFrequency=1");
failWith("-XX:ShenandoahGCMode=" + mode, "-XX:ShenandoahGCHeuristics=" + h, "-XX:-ClassUnloading", "-XX:-ClassUnloadingWithConcurrentMark", "-XX:ShenandoahUnloadClassesFrequency=1");
}
}
}